This study entails the development and methodology of use pulsed carbon dioxide laser systems (one was a prototype pulsed system with fiber optics delivery and the other was a modification of a commercial medical carbon dioxide laser), pulsed Nd:YAG laser coupled to a slit lamp, Q-switched Excimer laser and high-power CW Argon laser with fiber-optic delivery systems. These laser systems are being tested in a series of animal experiments to test the efficacy and safety of cutting vitreal membranes and of removal of atherosclerotic plaque from the intima of arteries. For the C02 and Nd:YAG laser systems systematic studies of animal vitrecomies were performed in order to characterize laser pulse characteristics necessary to transect vitreal membranes. Additional studies of retinal damage as a function of pulse characteristics and distance of cutting site from the retina clarified the potential for use of these laser systems close to the retina. For all laser systems systematic studies of tissue damage on human coronary arteries are in progress to characterize the feasibility (and optimal system design) of laser angioplasty. Evaluation of prototype fiber-optic angioscopes in pigs is being corried out in order to fully explore all facets of technology necessary for clinical laser angioplasty. Preliminary data reveal that the carbon dioxide laser can cut experimentally created membranes in rabbits for virtually any condition of the clarity of the optical media. The Nd:YAG laser pulses can cut vitreal membranes when power densities exceeding 1 GW/cm2 are achieved at the target. Moderate to severe turbidity of the optical media greatly decreases the ability to cut vitreal membranes with the Nd:YAG laser and creates the potential for increased retinal damage.